Performance of a wireless communication system can be measured, among other things, in terms of speech quality. In the current art, there are two techniques of speech quality assessment. The first technique is a subjective technique (hereinafter referred to as “subjective speech quality assessment”). In subjective speech quality assessment, human listeners are typically used to rate the speech quality of processed speech, wherein processed speech is a transmitted speech signal which has been processed at the receiver. This technique is subjective because it is based on the perception of the individual human, and human assessment of speech quality by native listeners, i.e., people that speak the language of the speech material being presented or listened, typically takes into account language effects. Studies have shown that a listener's knowledge of language affects the scores in subjective listening tests. Scores given by native listeners when lower in subjective listening tests compared to scores given by non-native listeners when language information in speech is defect, i.e., mute. In a normal telephone conversation, the listener is often a native listener. Thus, it is preferable to use native listeners for subjective speech quality assessment in order to emulate typical conditions. Subjective speech quality assessment techniques provide a good assessment of speech quality but can be expensive and time consuming.
The second technique is an objective technique (hereinafter referred to as “objective speech quality assessment”). Objective speech quality assessment is not based on the perception of the individual human. Some objective speech quality assessment techniques are based on known source speech or reconstructed source speech estimated from processed speech. Other objective speech quality assessment techniques are not based on known source speech but on processed speech only. These latter techniques are referred to herein as “single-ended objective speech quality assessment techniques” and are often used when known source speech or reconstructed source speech are unavailable.
Current single-ended objective speech quality assessment techniques, however, do not provide as good an assessment of speech quality compared to subjective speech quality assessment techniques. One reason why current single-ended objective speech quality assessment techniques are not as good as subjective speech quality assessment techniques is because the former techniques do not account for language effects. Current single-ended objective speech quality assessment techniques have been unable to account for language effects in its speech assessment.
Accordingly, there exists a need for a single-ended objective speech quality assessment technique which accounts for language effects in assessing speech quality.